there is another way although sort of expensive .I had a buddy that would go buy about 5 or 6 lbs of minnows and turn them loose in his 3 acre pond once a month sort of like feeding catfish. It seemed to work some as he was always catching good ones and not as many smaller ones. Then he up and moved so I figure it went bad once the minnows were cut off!! Another sign of over population is big saucer eyes on small fish .When they stunt the eyes will almost be larger than a nickel